2.2 Evaluating ecosystem services of alpine grassland
Plateau pika disturbance often produces many bare soil patches nested in alpine grasslands (Wilson & Smith, 2015; Yu et al., 2017b; Zhao et al., 2019). The plot scale was suggested to better reflect the effects of plateau pika disturbance on plant biomass and soil properties (Pang et al., 2020a, 2020b) because it can simultaneously consider the heterogeneity of soil properties in the presence of plateau pikas and the difference in plant biomass and soil properties between areas with and without plateau pikas (Pang et al., 2020b). Therefore, this study used a plot scale to examine plateau pika disturbance and its disturbance intensity in relation to forage availability, water conservation, carbon sequestration and soil nutrient maintenance services and used a quadrat scale to examine plateau pika disturbance and its disturbance intensity in relation to the biodiversity conservation service. Although there were many kinds of bare soil patches in the alpine grasslands, this study was restricted to the bare soil patches induced by plateau pikas. In the presence of plateau pikas, the soil water storage, soil organic carbon, soil total nitrogen, phosphorus and potassium stocks were calculated in the bare soil surface and vegetated surface, respectively.
In this study, the forage availability service was estimated by palatable plant biomass (Martínez-Estévez et al., 2013). The biodiversity conservation service was estimated by plant species richness (Wen et al., 2013). Water conservation services can be assessed by soil water storage (Ouyang et al., 2011). The carbon sequestration service can be evaluated by the soil organic carbon stock (Wen et al., 2013). Soil nutrient maintenance services can be assessed by soil total nitrogen, phosphorus, and potassium stocks (Wen et al, 2013).